Coating systems consist of a substrate and at least one coating layer overlying said substrate. In gas turbine construction, for example, substrates must be protected from excessively high temperatures and/or corrosive attack. This protection can be provided by depositing metal with a honeycomb structure on the substrate, said structure being filled with a ceramic and said ceramic essentially performing the protective function. The metal of the honeycomb structure is used for mechanical stabilization of the ceramic. However, the mechanical connection of the ceramic and the internal surfaces of the honeycomb structure is not good, causing the ceramic to continually peel off.
U.S. Pat. No. 5,634,189 describes a system having a porous internal structure formed by spherical elements of various diameters, said porous inner core being surrounded by a non-porous outer shell. The outer shell is not used for protection. The porous core is used for filling the cavity in order to achieve a degree of mechanical stability, the thickness of the porous core, however, being less than that of the shell in order to save weight.
U.S. Pat. No. 5,720,597 shows a gas turbine blade, at least part of the interior of which has a foam section.
U.S. Pat. No. 6,299,935 discloses a method for producing a coating wherein a suspension consisting of foam and a metallic powder is deposited on the surface of a substrate.
However, all the known systems or methods have the disadvantage that the mechanical connection between metal and ceramic is inadequate.